Effect of Grain Size on Amplitude-Dependent Internal Friction in Polycrystalline Copper
Effect of Grain Size on Amplitude-Dependent Internal Friction in Polycrystalline Copper
复制标题
晶粒尺寸对多晶铜中振幅相关内摩擦的影响
DOI：
10.2320/jinstmet1952.55.8_848
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发表时间：
1991
影响因子：
--
通讯作者：
S. Asano
中科院分区：
文献类型：
--
作者：
H. Goto;Y. Nishino;S. Asano
采用弯曲振动的自由衰减法，测量了不同晶粒尺寸的多晶铜内摩擦随应变幅值的变化规律。随着晶粒尺寸的减小，振幅依赖曲线向更高的振幅偏移。根据微塑性现象学理论对数据进行分析，并将其转化为典型的力学响应，如微塑性应变作为应力的函数。微塑性流变应力随晶粒尺寸的减小而增大，其规律与宏观塑性变形相似。而微塑性流变应力随晶粒尺寸的变化要远大于宏观塑性流变应力。1×10−9塑性应变下的流变应力不能用Hall−Petch关系（晶粒尺寸的平方根反比的简单线性函数）来表示，当晶粒尺寸大于80μm时流变应力基本不变。这意味着在表面的影响下，粗晶试样中单个晶粒对周围晶粒的约束力显著降低。然而，随着塑性应变的增加，微塑性流变应力表现为接近Hall - Petch关系。
Internal friction in polycrystalline copper varying grain size was measured as a function of strain amplitude at around 700 Hz by means of the free decay method of flexual vibration． The curves of the amplitude dependence are found to shift to higher amplitude with decreasing grain size． The data are analyz− ed on the basis Of the phenomenological theory of microPlasticity and converted into typical mechanical responses such as the microplastic strain expressed as a function of stress． The microplastic flow stress in− creases with decreasing grain size in a similar way to macroplastic deformation． However， the variation of microplastic flow stress with grain size is much greater than that of macroplastic flow stress． The flow stress at the plastic strain of 1×10−9 cannot be expressed by the Hall−Petch relation， a simple linear function of the inverse square root of grain size， and is almost constant when grain size is larger than 80μm． This means that the constraining force of an individual grain by surrounding ones markedly decreases in coarse−grained specimens under the influence of surfaces． As the plastic strain increases， however， the microplastic flow stress appeares to approach the Hall−Petch relation．